openCV4Android 功能2d 错误

Question

我想使用features2d在两个图像之间绘制良好的匹配（不是所有匹配）。所以我使用了这段代码：

Mat gray1 = //image1 converted to gray
Mat gray2 = //image2 converted to gray
MatOfDMatch matches = new MatOfDMatch();
MatOfDMatch gm = new MatOfDMatch();
LinkedList<DMatch> good_matches = new LinkedList<DMatch>();
MatOfKeyPoint keypoints_object = new MatOfKeyPoint();
MatOfKeyPoint keypoints_scene = new MatOfKeyPoint();
Mat descriptors_object = new Mat();
Mat descriptors_scene = new Mat();
FeatureDetector fd = FeatureDetector.create(FeatureDetector.ORB);
fd.detect(gray1, keypoints_object);
fd.detect(gray2, keypoints_scene);
// – Step 2: Calculate descriptors (feature vectors)
DescriptorExtractor extractor = DescriptorExtractor
.create(DescriptorExtractor.ORB);
extractor.compute(gray1, keypoints_object, descriptors_object);
extractor.compute(gray2, keypoints_scene, descriptors_scene);
DescriptorMatcher matcher = DescriptorMatcher
.create(DescriptorMatcher.BRUTEFORCE_HAMMING);
matcher.match(descriptors_object, descriptors_scene, matches);
double max_dist = 0;
double min_dist = 100;
List<DMatch> matchesList = matches.toList();
// – Quick calculation of max and min distances between keypoints
for (int i = 0; i < descriptors_object.rows(); i++) {
    Double dist = (double) matchesList.get(i).distance;
    if (dist < min_dist)
    min_dist = dist;
    if (dist > max_dist)
    max_dist = dist;
}
for (int i = 0; i < descriptors_object.rows(); i++) {
    if (matchesList.get(i).distance <= 3 * min_dist) {
        good_matches.addLast(matchesList.get(i));
    }
}
gm.fromList(good_matches);
List<KeyPoint> keypoints_objectList = keypoints_object.toList();
List<KeyPoint> keypoints_sceneList = keypoints_scene.toList();
MatOfKeyPoint matOfObjectGoodKeyPoints = new MatOfKeyPoint();
MatOfKeyPoint matOfSceneGoodKeyPoints = new MatOfKeyPoint();
LinkedList<KeyPoint> listOfObjectGoodKeyPoints = new LinkedList<KeyPoint>();
LinkedList<KeyPoint> listOfSceneGoodKeyPoints = new LinkedList<KeyPoint>();
for (int i = 0; i < good_matches.size(); i++) {
    listOfObjectGoodKeyPoints.addLast(keypoints_objectList
    .get(good_matches.get(i).queryIdx));
    listOfSceneGoodKeyPoints.addLast(keypoints_sceneList
    .get(good_matches.get(i).trainIdx));
}
matOfObjectGoodKeyPoints.fromList(listOfObjectGoodKeyPoints);
matOfSceneGoodKeyPoints.fromList(listOfSceneGoodKeyPoints);
// feature and connection colors
Scalar RED = new Scalar(255, 0, 0);
// output image
Mat outputImg = new Mat();
MatOfByte drawnMatches = new MatOfByte();
// this would draw good matches,but not works fine:
Features2d.drawMatches(gray1, matOfObjectGoodKeyPoints, gray2,
matOfSceneGoodKeyPoints, gm, outputImg, Scalar.all(-1), RED,
drawnMatches, Features2d.NOT_DRAW_SINGLE_POINTS);

但在运行时，会发生此错误：

CvException ...Features2D/src/draw.cpp：208： 错误： （-215） i2>= 0 && i2 < static_cast（关键点2.大小（））

代码中有什么问题？

Answer 1

问题是，你给出了一个过滤列表（即 matOfSceneGoodKeyPoints ） 到 drawMatches() 。但良好匹配列表gm包含基于原始列表的索引。所以改为

Features2d.drawMatches(gray1, keypoints_object, gray2,
keypoints_scene, gm, outputImg, Scalar.all(-1), RED,
drawnMatches, Features2d.NOT_DRAW_SINGLE_POINTS);

你有你想要的。抽签的比赛仍然仅限于最好的比赛，因为只使用gm中的比赛。